marfrit 5c69460722 ffmpeg-v4l2-request-fourier: restore AV_CODEC_FLAG_LOW_DELAY in H.264 decoder
FFmpeg 8.x dropped the H.264 decoder's low_delay code path —
AV_CODEC_FLAG_LOW_DELAY no longer prevents h264_select_output_frame
from running the display-order DPB output queue.  The daedalus-v4l2
daemon's `ctx->flags |= AV_CODEC_FLAG_LOW_DELAY` at
daemon/src/decoder.c:202 has been a silent no-op since the SONAME
61→62 jump landed in reauktion/daedalus-v4l2 PR #16; on Firefox
YouTube this re-introduced the 2-1-4-3 B-frame pair-swap that PR
#12's daemon flag was supposed to prevent.

Fix lives in libavcodec, not the daemon: restore the documented
LOW_DELAY semantics so the daemon (and any other V4L2-stateless-
style consumer) keeps the one-frame-per-send_packet decode-order
output contract it already declares.

## Patch

0006-h264-restore-low-delay.patch touches libavcodec/h264_slice.c:

- h264_select_output_frame: early-exit when LOW_DELAY is set.
  Emit the just-decoded picture as next_output_pic, mirror the
  corruption / recovery-point tracking the main path performs,
  skip delayed_pic[] / POC reorder machinery entirely.

- h264_field_start: suppress the SPS-driven
  `has_b_frames = sps->num_reorder_frames` clobber when LOW_DELAY
  is set.  Without this the per-slice bitstream_restriction_flag
  re-pickup would reintroduce a nonzero reorder buffer mid-stream
  even after the daemon set has_b_frames=0 at avcodec_open2.

## Why not daemon-side

A daemon SPS-rewrite (`num_reorder_frames=0`) was considered but
rejected: it works only for the daemon's reconstructed SPS NAL,
not for any in-band SPS the daemon dlopens libavformat to parse
in other code paths.  Restoring documented FFmpeg flag semantics
is the smaller, more durable change and keeps the daemon
interface stable.

## Packaging

- PKGREL/pkgrel bump to 9.
- No new build-deps, no Depends change.
- Substitution arc cycles 6/7/8 unchanged.

## Refs

- reauktion/daedalus-v4l2#11 / #12 (LOW_DELAY half-measure on
  daemon side, originally landed against FFmpeg 7.x).
- daemon/src/decoder.c:202 (`ctx->flags |= AV_CODEC_FLAG_LOW_DELAY`
  for H.264 only — unchanged, but now actually has effect again).
2026-05-22 14:20:37 +02:00

marfrit-packages

Overlay package repository for the reauktion.de infrastructure.

Published at: https://packages.reauktion.de/

Scope

Tree Arches Notes
Arch Linux ARM (ALARM) aarch64 primary target — Pi 5, Rock 5, ampere, KU-1255 test rigs
Arch Linux x86_64 for nuccies / workstations
Debian arm64, amd64 for non-Arch hosts

MIPS is intentionally unsupported. The Fritz!Box is sacred.

Layout (served at packages.reauktion.de)

packages.reauktion.de/
├── arch/
│   ├── aarch64/{marfrit.db,marfrit.files,*.pkg.tar.{xz,zst}{,.sig}}
│   └── x86_64/...
├── debian/
│   ├── dists/
│   │   ├── bookworm/{Release,InRelease,Release.gpg,main/binary-{arm64,amd64}/...}
│   │   └── trixie/...
│   └── pool/main/...
└── marfrit.gpg      # public signing key

Adding the repo (Arch / ALARM)

curl -sO https://packages.reauktion.de/marfrit.gpg
sudo pacman-key --add marfrit.gpg
sudo pacman-key --lsign-key 92D5E96D8F63C75E4116AA1FF5C8C4603D0D250C

# Paste at the end of /etc/pacman.conf:
[marfrit]
Server = https://packages.reauktion.de/arch/$arch
SigLevel = Required DatabaseRequired

sudo pacman -Sy

Adding the repo (Debian)

sudo install -m 755 -d /etc/apt/keyrings
curl -s https://packages.reauktion.de/marfrit.gpg | \
    sudo gpg --dearmor -o /etc/apt/keyrings/marfrit.gpg

echo "deb [signed-by=/etc/apt/keyrings/marfrit.gpg] https://packages.reauktion.de/debian $(lsb_release -cs) main" | \
    sudo tee /etc/apt/sources.list.d/marfrit.list

sudo apt update

Signing key

  • Fingerprint: 92D5E96D8F63C75E4116AA1FF5C8C4603D0D250C
  • UID: Markus Fritsche (marfrit-repo signing) <mfritsche@reauktion.de>
  • Expires: 2030-04-13

Key management procedures (renewal, rotation, revocation) live in DokuWiki at private:reauktion:marfrit_repo_key (admin-only).

Layout in this Git repo

marfrit-packages/
├── README.md
├── arch/
│   └── distcc-avahi/                # ALARM distcc with --with-avahi
├── debian/                          # (future) Debian source packages
└── .gitea/
    └── workflows/
        └── build.yml                # CI pipeline stub

Mail

mfritsche@reauktion.de.

S
Description
ALARM aarch64 + Arch x86_64 + Debian arm64/amd64 overlay repo — published at packages.reauktion.de
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